We propose to organize a series of three yearly meetings devoted to definition and measurement of hyperkinetic movement disorders in childhood. The taskforce on childhood motor disorders has previously established consensus definitions and measurement technology recommendations for hypertonic disorders and negative signs. Hyperkinetic disorders represent the third major category of pediatric motor disorders. In the first of the three meetings, consensus definitions relevant to children will be established for the terms "chorea", "choreoathetosis", "hyperkinetic dystonia", and "tremor". In the second meeting, current scales and technology for diagnosis and quantification of these impairments will be discussed. In the third meeting, new scales and technology for diagnosis and quantification will be demonstrated. The result of this series of meetings will be a consensus statement on definitions, identification of gaps in current assessment tools, and specific recommendations for the development of new measurement tools. Definitions and measurement tools are essential for communication between clinicians, inclusion of children in clinical trials, and measurement of outcomes of treatment in the clinic and in clinical trials. This project will provide consensus definitions and work toward the development of measurement tools for children with hyperkinetic disorders. The result will be definitions and recommendations that will improve the effectiveness and success of clinical trials for children with disorders of movement.